These abandoned Mayans cities hold an alarming prophecy for today

At the height of the Mayan empire 1,400 years ago, the city of
Tikal in modern-day Guatemala was a bustling metropolis the size
of London during the Middle Ages.

But when the Spanish conquistadors arrived in Central America in
1517, the Mayan people had left Tikal for the surrounding jungle,
and its limestone towers were already in ruins. At this point, the city
had been abandoned for several hundred years.

But why did a sophisticated and seemingly prosperous
civilization would pull up stakes over the course of just two
centuries, abandoning their urban centers?

A civilization dries up

By the time of Tikal's decline sometime around 900, Maya
civilization and culture had been developing for at least
1,000 years and the empire had amassed an estimated population of 19 million.
Droughts were common, but an innovative reservoir system allowed Tikal to
flourish anyway, eventually growing to as many as 100,000
residents.

But a 2012 study in the journal PNAS found that just when it was
reaching its peak, the entire region ruled by the Maya
began suffering droughts — at
least eight in the century of Tikal's decline.

iStock

During these dry
periods, the area saw rainfall reduced by as much
as half, even in the wet season. These intense droughts
could last up to 18 years.

There's also strong evidence
that the Mayan approach to forestry and water management could
have added to the the dry spells.

Their methods may have worked
while cities were still growing, but when the population
density reached 2,000 people per square mile — similar to that
of Los Angeles — the Maya were engaged in a massive
clear-cutting of the surrounding forests, unintentionally
amplifying drought conditions.

How does that work?

While the rainwater Mayan cities depended on for drinking and
irrigation was becoming more and more scarce, they were also
clear-cutting their forests using a "slash-and-burn" technique similar to the one used
today. The method is exactly what it sounds like: They cut
down the surrounding jungle and set it ablaze to make room
for crops.

Deforestation in Brazil.Mario Tama/Getty

Fields absorb less heat from the sun. While that sounds
like that might keep the surrounding areas cool, it actually
has the opposite effect: Less water is evaporated out of the
ground, meaning the rain cycle has less water to create clouds
and, eventually, precipitation.

Tough times also probably exacerbated the ongoing social and
political strife, and, even worse, Mayan city-states
were warring with their neighbors.

Amid all this strife, it's pretty easy to see why residents of
the southern part of the empire would abandon their bloated
cities for smaller and more sustainable agricultural villages.
The southern lowlands of the empire never recovered.

Northern cities like Chichen Itza, experienced a slump
but carried on for another century or so. But sometime
before 1000 and 1100, the worst drought in 2,000 years hit the region.
It was, more or less, the death knell for the great Mayan cities.

Kulkulcan
castle at Chichen Itza, one of the Seven Wonders of the Modern
World.Heriberto
Rodriguez/Reuters

What's that have to do with us?

Large-scale deforestation has been tied to present-day
global warming, and the effects could be as crippling as
they were to the Mayans — but on a much, much larger scale.

Severe droughts, like the ongoing dry spell in
California, are becoming more and more common as a result of
climate change. A mega-drought lasting decades is expected
to grip the southwestern US by the end
of the century.